Silsilah as-Sahihah 3251 — Abu Bakr (ra) was the immediate caliph

Lady Aisha (may Allah be pleased with her) says: When the illness of the Messenger of Allah (peace and blessings be upon him) intensified, he ordered (my brother) Abdur Rahman bin Abu Bakr to "bring a tablet or a bone, so that I may write something regarding Abu Bakr (may Allah be pleased with him), so that no one will differ about it." When Abdur Rahman went away, the Prophet (peace and blessings be upon him) said: "Abu Bakr! Allah Almighty and the believers have refused that there should be any disagreement concerning you."